In a statement on Monday, the Royal Thai Army said Cambodia’s actions “constitute provocation and a violation of measures aimed at reducing tensions”, adding that they were “inconsistent” with the terms of the ceasefire.
It also said it “may need to reconsider” the release of 18 Cambodian soldiers held in Thailand since July.
Thailand would be “obliged to act in accordance… [if] violations of agreements and national sovereignty continue”, it added.
Cambodia has not yet commented.
It comes just hours after China’s Foreign Minister Wang Yi praised the “hard-won” ceasefire, and US President Donald Trump praised the “rapid and fair conclusion”.